fdo#72850: ODF export: don't export spurious style:display="false"

... on style:header-left, style:header-first, style:footer-left,
style:footer-first.

(regression from d92345561c998f7382cf9ef0fdcd29096f978435)

Change-Id: I48c51fcd2b07ae8b0e3ec2c1087a388c6900b366